public class Main {
    public static void main(String[] args) {
        System.out.println(func1(6));
    }
    public static int func1(int n){
        if(n==1) return 1;
        if(n==2) return 2;
        if(n==3) return 4;
        int[] dp=new int[n+1];
        dp[1]=1;
        dp[2]=2;
        dp[3]=4;
        for(int i=4;i<=n;i++){
            dp[i]=dp[i-1]+dp[i-2]+dp[i-3];
        }
        return dp[n]%1000000007;
    }
}